Some aspects of the fabrication of structures for use in the electronics industry require the formation of holes in a substrate. One method for forming such holes is to physically punch the holes in the substrate. Typically, the substrates are thin films.
Frequently, the punching of holes occurs while the punching device and the substrate move relative to each other. The movement of the punching device and the substrate may take place in both the X and Y directions. That is, movement may take place parallel to the plane of the substrate. Such movements along the axial directions are referred to as "punch-on-the-fly X" (POFX) and "punch-on-the-fly Y" (POFY).
During both POFX and POFY operations, there is at least some lateral component of movement of the punch and/or the substrate, or film or web, relative to each other while the punch is actually within the substrate, during the punch "in web time". This time interval is referred to as the web engagement time and refers to the interval during which the punch is mechanically engaged with the hole. The magnitude of the relative motion of the punching device and the substrate during this interval is dependent upon the velocity of the relative movements.
As a punch is used to produce holes in a substrate, it generates fine particles, much as a saw blade generates dust. These fine particles gather on the punch and punch guides, causing frictional drag on the movement of the punch. This problem is particularly important with punches that have slow actuation cycles. The debris can cause the actuation cycles to slow.
Clogging of punch guides, causing frictional drag on the movement of the punch, is also a particularly potentially damaging problem with POFX and POFY systems. For example, as the punch movement is delayed, the substrate and punch assembly continue to move relative to each other. This initially may cause only hole quality problems. However, as time goes on, the delayed punch movement can rip the substrate. Ripping of a substrate may necessitate discarding the entire substrate, or web or film. This can be a particularly costly problem, especially when ripping occurs near the end of a long web or film structure, but still results in discarding the entire web or film.
The frictional drag caused by a buildup of substrate material in the punch assembly can delay the initial stroke of the punch. The frictional drag may also delay the return stroke of the punch. In the most severe cases, the frictional drag on the movement of the punch may cause a failure of the punch to return at all.
Slowing of the punch cycle may also be caused by other conditions, such as punch and die edge wear. These wear conditions also increase the energy required to pierce the film, thus slowing the punch and decreasing the rebound velocity.
In view of the above, it is apparent that problems caused by punch slowdown, regardless of the cause, are costly problems.